Wax On, Wax Off: A Guide To Fossil Vertebrate

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Wax On, Wax Off:A Guide to Fossil Vertebrate MicropreparationScott K. MadsenDecember, 2009

Table of ContentsIntroduction . 1What is Microprep?. 1“Wax on, wax off” - the Micropreparator mindset . 2What is the goal? . 3Tools, Equipment, and Workspace . 3Tables. 4Chairs . 5Air lines . 5Microscopes (and accessories) . 5Light sources. 6Hand Tools . 6Carbide. 7Forceps. 8Your personal kit . 8Conservation Philosophy . 8Consolidants and Adhesives: Solvent-based systems vs. Cyanoacrylates . 10Techniques and Tips . 11How to position your body and equipment . 11Removing matrix . 12Using adhesives . 13Carbowax and Cyclododecane . 14Mounting and storing microfossils . 14Summary . 15Acknowledgements . 15References and Resources. 15List of FiguresFigure 1. My work set-up at Dinosaur National Monument. . 4Figure 2. Magnified view of sharp point of carbide needle. Pencil for scale. . 7Figure 3. Magnified view of beveled edge of carbide needle. Edge of quarter for scale. . 7Figure 4. Hand configuration where position of thumbs act as a brace and stop. . 12Cover IllustrationView of an in-prep Sphenodont skull from the Jurassic age Morrison Formation, Utah; the skullis slightly larger than a thumbnail.

INTRODUCTIONIn 1996, Rich Cifelli edited “Techniques for Recovery and Preparation ofMicrovertebrate Fossils” (see References) which included a section I wrote called “SomeTechniques and Procedures for Microvertebrate Preparation” dealing with manualpreparation. That paper contains a lot of “how to” detail regarding specific materials andtechniques and sources for equipment and materials that are still relevant. However, overten years later, I am still frequently asked for advice on buying tools for microprep, howto set up a work station, and what techniques to use. This happens often enough that Idecided it’s time for an update. This Guide is an introduction to microprep whichemphasizes what I consider to be the most important components of microvertebratepreparation. Most of my suggestions are presented more or less in the sequence that Ifollow when I approach a project. Please refer to my 1996 (a and b) papers for morespecific techniques and applications.This Guide is aimed mostly at beginners who are already comfortable with the basics ofpreparation. If you have spent time using non-pneumatic hand tools, so much the betterbecause Micro-jacks and the like are seldom a part of microprep. Microprep is aboutadjusting and adapting to a different scale; think small, very small. Also, the subject ofmicroprep inevitably leads to more philosophical musings about preparation,conservation, and other non-technical aspects of the work. These things are just asimportant as technical skill with a needle, so, if you’re new to this field, please bear withme. Beginners take note: my recipes for success are by no means the only way and Iencourage you to seek out as many alternative sources of information and techniques aspossible; some are referenced in the text and others follow in References and Resources.WHAT IS MICROPREP?Micropreparation (herein referred to as “microprep”) is any manual preparation ofvertebrate fossils on a scale that virtually requires the use of a microscope. Perhaps it isby simple virtue of the scale that microprep can be so compelling and impressive to theuninitiated. This is especially true of those not familiar with the concept that the tiniestof creatures coexisted with the largest dinosaurs on the planet. During my 20 year tenureat Dinosaur National Monument I “performed” live microprep through the use of amicro-video camera attached to my Nikon SMZ-U microscope while I worked on variousMesozoic mammals, frogs, lizards, and other tiny creatures. One of my favorite trickswas to focus on the tip of a single denticle of a baby theropod tooth and zoom back untilthe public could see the whole tooth mounted on a pin head. At first a single denticlewould fill the whole monitor, a clear but incomprehensible image, and as the rest of thetooth slowly appeared people would recognize what they were seeing and gasp inastonishment; you could actually hear a wave of recognition pass through the crowd!Here was a dinosaur tooth the size of a sand grain and they couldn’t have been morefilled with wonder if they were looking at the largest dinosaur. This was showmanshipand the public loved it, but the real value was that it never failed to draw them into theworld of the very small. It was a hook to capture the public’s fascination and then teachthem about extinct ecosystems and the art of fossil preparation.1

“Wax on, wax off” - the Micropreparator mindsetNo, the title to this paper does not refer to Carbowax, paraffin, or beeswax. It refers tothe degree of focus, control, and discipline required to practice microprep and how thatcan have a meditative, almost Zen-like quality to it. This was illustrated to me one day in2007 when one of my interns, Tom Nelsen, spent many hours learning the joys of carbidesharpening (the first skill I teach students, in part because it weeds out those who lackpatience and persistence). After hours of trial and error, I heard him muttering “wax on,wax off, wax on, wax off ” If you’re not familiar with this phrase, check out the firstKarate Kid movie and you’ll better understand Tom’s mantra; he was acknowledging thedegree of focus, concentration, and repetition required to master the most basic skill ofmicropreparation.People have often remarked to me that they think microprep must be much harder thanwork on macrofossils. I think it is just different. The preparation of either very tiny orvery large bones (or, as George Engelmann once referred to them, “the ridiculous to thesublime”) requires their own set of techniques, tools, and materials. To do either of themwith consistent high-quality results takes equal parts of skill and experience. But onething that sets microprep apart from the rest of the crowd is that it tends to be veryunforgiving of even the slightest lapse of attention or slip of the needle. We can get awaywith little dings and scrapes in a large sauropod femur, but when the femur is only acentimeter long and one millimeter wide, a small mistake can obliterate the specimen. Inthis regard, it can be very intimidating, especially for a beginner. A little bit of fear andtrepidation is good until you get the hang of it; just don’t let that fear paralyze you.Having said that, realize that some folks just aren’t cut out for microprep. It requires longhours at the scope sitting virtually stone-still except for the barely perceptible flex of afinger and thumb and, in the course of a day, progress may be impossible to detect withthe naked eye. Not everyone has the kind of mindset it takes to pursue this work. Ifthat’s not you, that’s okay; there are plenty of big bones to work on.There is a grey area that should be mentioned at this time: the instances when one mayuse a microscope (and other concepts mentioned here) applied to macro-fossils. PerhapsI am a perfectionist, but I happen to be one of those types who is haunted by those straybits of distracting matrix left on otherwise clean femurs or in the deep recesses ofiguanodon braincases. They just bug me and I have to get rid of them even if it takes amicroscope and a carbide needle to do it. The same is true with removing overly thick(and unnecessary) glue coatings from modest sized bones or working out the fine detailsof the intricate tongue and groove structures of bone sutures on larger skulls. What maybe considered overkill prep to some often means the difference between being able toreadily distinguish between mere cracks and a real suture. To me it is also the differencebetween a good prep job and a great prep job. I want people to ooh and ah when they seemy work and you should want that, too.2

WHAT IS THE GOAL?Before any work begins you should ask what the goal of the preparation is. Determine,as early as possible, how the specimen will ultimately be “presented.” This decisionshould involve consultation with researchers or others and may depend much on what cansafely be done (your call), whether or not the specimen is to be cast, photographed withSEM, or other purposes the researcher has in mind (their call). Researchers can be prettydemanding sometimes so be prepared to stand your ground when they ask the impossibleor be ready to hand the specimen over to someone else who is better qualified.Questions to ask: Can the specimen be entirely freed of matrix and is this desirable? Isthe specimen best prepared on one side (in relief)? Which side is “best” for display orresearch purposes? How are you going to hold the specimen as prep proceeds (will youhave to leave or even create a “handle” and where should it be)? Will you need to useCarbowax or other materials for a temporary matrix and what are the consequences?What is the best/safest way to store the specimen? I hate to have to add this too, but myexperience has been that you’ll need to consider the best way to protect the specimenfrom the abuse of those people less careful than you; I love preparing a specimen the firsttime but I dislike repairing them!TOOLS, EQUIPMENT, AND WORKSPACEI have seen some pretty amazing field prep done on microfossils by experienced handswith just a hand lens and a piece of carbide. However, at some point, no matter howgood you are, you can only be as good as your equipment allows you to be (take noteresearchers and those who hold the purse strings). If you have a junky microscope andpoor lighting, your work results are going to be poor. Trying to learn how to domicroprep with substandard tools can be brutally frustrating and I have seen somepotentially good preparators give it up because of this obstacle. What is worse is thatmany don’t even know their tools are substandard. Most of these folks have simply neverbeen exposed to a good microscope, light-source, or carbide.I approach every microfossil with the attitude that I’ve got one shot at getting it right. Tobe handicapped by lousy equipment in a professional lab is simply an absurd concept. Itmakes no sense to invest a fortune (relatively speaking) in collecting specimens only toneglect the lab work that follows. Most hand tools are relatively cheap (Foredomgrinders, carbide rod, Carbowax, etc); a good microscope and light source are not cheapbut they are essential for a lot of our work. To paraphrase Bill Amaral (1989), your prepmicroscope should be at least as good as that of the researcher’s microscope (maybe evenbetter).When I enter a lab to make recommendations for a microprep setup, the first thing I do isgo to the work table and check out the scope, light-source, type of needles being used andthe sharpener for those tools; pretty much everything else is secondary to these essentialtools. When I look through the scope and see a dim hazy image and a blunt hypodermicneedle sitting nearby I recoil.3

On the other hand, to be quite frank, I am all too often dismayed when I walk into labsand witness the sorry condition of equipment and tools that many people use. I’mreferring to air tools lying in the sand tables, gunked up glue bottles laying on their sideswith more glue on the outside of the container than in them, etc. Take pride in your workand take care of your tools! If you do, maybe your employer will be more likely to buyyou better ones!For more information and illustrations regarding tools, equipment and setting up amicroprep workspace, see Amaral (1989), the links in References section, and also seemy setup (Fig. 1).bbadcFigure 1. My work set-up at Dinosaur National Monument. Notice the followingequipment: sturdy table, comfy adjustable chair, adjustable boom stand (a), fiber opticlight (b), selection of sharpened carbide needles (c), and moveable work surface (d).The air line is not readily visible in the wires coiled on the boom stand. Also notice therelaxed shoulders and neck, a result of correct work surface and eye-piece heights.TablesFirst and foremost, you need a solid vibration-free work surface. The same is true forwhatever surface your scope and light-source are mounted on, whether it is the sametable or the wall. Stability is everything. I prefer a heavy table with one or more sturdyshelves in front of me and to the sides: these provide a variety of surfaces for holdingeverything from light sources to vials as well as attachments for air lines and powercords. A rail mounted flush with the sides and back of the table is a good idea for helpingto capture bits of bone or teeth that fly away during prep – and I can guarantee they will.4

I find there is no such thing as too many electric outlets as well. Velcro is a great way ofkeeping electric cords and air lines out of the way.ChairsInvesting in a good chair will improve your comfort, stamina and precision. It does nothave to be an expensive chair, but it should be very adjustable. You should be able toposition yourself relative to the microscope eye-pieces so that you don’t have to strainyour body to see. Adjustable arms can be very useful for bracing and stability. I havebeen in too many labs where the chairs people are using are junkers compared to thoseused by the secretary or computer jock in the next room. Ergonomic furniture is not justa luxury; it can improve stamina and the quality of your work and help prevent injuries.Air linesI use pneumatic tools for microprep on very rare occasions (usually I have been sorry thatI did). But an air line is incredibly useful for blowing away matrix from the specimen.This little addition is worth its weight in gold for the trouble it will save you keeping thespecimen free of debris. Without one you are stuck having to hold a squeeze bulb all thetime or blow with your lips (each is inconvenient and/or poses risk to the specimen).Arrange for compressed air at the workstation that aims a gentle and narrow air stream atthe work. I mount my line to one of the light pipes with Velcro so it’s pointed rightwhere I am working. Be sure to use a valve that allows just a little air to run through theline (have you ever seen those videos of an escaped fire hose? Been there, done that!). Itis also important to know when to turn the air off – be aware of loose pieces that may flyaway forever. Make sure the airline has a good desiccator – water buildup in the lineshas caused at least one disaster for me. Amy Davidson (1998) shows a schematic of achip-blowing (preparation) needle; with slight modifications, this concept can be used tobuild a stationary blower.Microscopes (and accessories)I am sure there are many great microscopes out there, but all I can say is that I miss myold Nikon SMZ-U that I had at Dinosaur National Monument. It had fabulous optics(with a stereo zoom range from 0.75x to 7.5x), a wide field of view and a flat image at allmagnifications (i.e. no curvature of field aberrations); these are all important qualities fora good microprep scope. The more whistles and bells you can afford the better. Thismeans a full complement of accessory lenses, including 0.5x – 2x objective lenses, 10x,15x and 20x eyepieces.People are always asking me how to upgrade a scope’s power. The most important thingto remember is that changing objective lenses to a greater power reduces the focal length(working distance for your fingers) between the lens and the specimen, so you mightwant to think first about getting more powerful eyepieces. A really great scope with allthe extras (like my SMZ-U) will cost up to 20,000. A serviceable scope for microprepcan be bought for a fraction of that, but my sense is that with optics you get what you payfor. Unfortunately, this primary piece of hardware is also the one most often lacking inlabs, usually because the cost is beyond that of many program budgets. One solution is to5

encourage a researcher who is serious about studying microfossils and has skill in grantwriting to include a good lab scope in their next grant proposal.Don’t forget to buy a protective lens for the objective lens so you don’t ding the glasswith matrix or debris when you are prepping or sharpening carbide. I get rid of therubber eye-guards on the eye pieces because they just make it harder to get my eyes“centered” properly, though many people find them necessary. I’m very diligent aboutkeeping my scope clean, especially the eye-pieces, and cover it every night or when notin use. Be extremely careful with how you clean glass lenses (especially the objective);they can cost a fortune!Get a heavy boom stand with long arms and universal mounts for the scope body so youcan turn and twist it to any angle and consider bolting the stand to the table so it doesn’ttip over from the weight of your scope (and all the accessories mounted to it). This canbe a real hazard; I learned the hard way when my scope crashed onto a specimen crushingit and almost taking out the objective lens, too. Bolting a stand down is preferable toweighting it with sandbags; bags tend to leak and they take up space better used for tools.For microprep in the middle of a large block invest in a mobile floor stand (like you seein hospital operating rooms) with a long articulating boom arm. These are worth theirweight in gold (some are about as valuable; prices range from about 650 to 3,000) andprevent the hassles and risks associated with finding a place to put your scope and lightsource on the block. Fiber optics also provide the option for extra long light pipes so youcan mount the light source on the boom stand and run the light pipe the length of thearticulating arm.There are some amazing cameras available today that can send high resolution images tomonitors for live action views, video and still image capture, and links to computers forstorage and manipulation of data. They are also just plain fun to use and are a great aid inteaching prep, educating the public, and documenting your work.Light sourcesForget about the old illuminators; they can produce a lot of heat and the light quality ispoor. For microprep you will need a variable intensity fiber-optic unit. Look fortwinned, long and supple light pipes with light-focusing lenses. I generally prefer a ringlight that fits around the outer rim of the objective lens because they don’t requireconstant adjustment. The idea is to get the light where you need it at all times. This isespecially true at high-magnification when you are trying to get that last bit of rock out ofa hard to reach place.Hand ToolsUse the best tools you can get your hands on! I got rid of hypodermic needles, sewingneedles, dental tools, and Exacto-knives years ago. Dental tools can be very useful in thefield, but for microprep the only use I’ve found for them is the occasional time I have toreach around a corner (usually this involves the inside of a skull) that can’t be reachedwith a straight carbide needle.6

CarbideCarbide is about the only metal on the market that has the strength to hold an edge welland will not “spring” when you apply or release pressure. Use high quality diamondsharpeners to get the proper edge for the job and keep them sharp! This takes somediscipline but is worth the trouble. And it is truly amazing how sharp a point you canmake with carbide (Figs. 2 and 3).Figure 2. Magnified view of sharp pointof carbide needle. Pencil for scale.Figure 3. Magnified view of beveled edge ofcarbide needle. Edge of quarter for scale.Carbide is available from several vendors, but I get mine from MSC Industrial Supply. Itis called “carbide rod, C-2 solid carbide”, and comes in many thicknesses (some vendorsuse inches and others use millimeters for measure so it can get confusing at times). Beaware there is “bad” carbide out there; if you see little cracks and voids appearing in it asyou sharpen it under the scope you should probably try another piece. I consider about1mm to be the best thickness for most microprep work; any thinner and it tends to breaktoo easily and much thicker of a rod is overkill and takes forever to grind to shape. Ibreak it to a reasonable length in my fingers and sharpen it under the scope using adiamond wheel mounted to a Foredom grinder with a variable speed foot control (this isabout the only use I have for the grinder). The best diamond wheel I have found for thispurpose is also from MSC (3/8” x 3/8”, 150 grit, diamond grinding pin, item# 03506128, 43.00). This wheel seems to cut faster and more smoothly than any other I have foundand they last a long time.Sharpening carbide might sound easy but actually requires a fair bit of patience andtechnique. I prefer to brace the Foredom handpiece on a pad at a slight angle to the tableand crank up the magnification until the abrasive wheel fills the field of view. Hold thecarbide rod at about a 20 ̊ - 30 ̊ angle to the top of the head and rotate it in your fingerand thumb; I move the carbide in and out along the surface to even out the wear on thehead. Gentle pressure is most effective so resist the urge to apply pressure. With 1mm7

carbide I generally start trimming at least ¼ inch from the tip to create a nice gradualtaper. For a super-fine point you will have to drop the carbide to a very low anglerelative to the diamond wheel. To bevel or shape the final tip, crank up the magnificationand adjust your tools to allow even more precise grinding.I’ll say it again. Keep tools sharp! Dull tools just make bigger holes when you screw upand tempt you to use pressure instead of precision. I start each morning with asharpening session. I typically have from 6 – 12 carbide needles on hand of variousgauges sharpened on both ends and with a variety of different-shaped tips to handlechanging rock conditions. I store them with one point down in a high-density foam padand sort them with the sharpest ones closest to me so I don’t have to hunt for what I needI seldom use pin vice holders for carbide in microprep except when I’m removing a lot ofrock with a thicker-gauge point. I get the highest control of carbide and best “feel” usingjust my fingers. You might want to try this. If you use a pin vice I’d recommend onewith a narrow tapered end as the wide ones can pose a hazard to the specimen when youare working up close in confined spaces as well as block your view.ForcepsAnother tool I always have close at hand is my Dumont needle-nosed forceps. I’ve hadthe same pair for over 30 years, in part because I use them for picking things up, notdigging around in cracks. They are lightly sprung and great for picking up the tiniest ofbones and teeth. The finer the tip the tinier the object you can pick up without eithercrushing it or launching it across the room. I am not a fan of vacuum tweezers as they arecumbersome and tend to have too large tips for most micro-work.Your personal kitIf you are serious about this business, get your own personal tools. This may soundharsh, but I recommend having your own set of tools and don’t let other people mess withthem. The first job I ever had was working in a restaurant and I can still rememberwatching the head chef come in every morning and opening his own briefcase full offancy knives; I now understand why. Most tools develop personalities (the diamondsharpening wheel is one of them) that you get to know well and other folks tend to screwthem up. The most important tools in my kit are the carbide needles and diamondsharpener. I came in one morning and found someone sharpening an Estwing hoe-pickwith my diamond bit – I could have killed him! Hide your tools if you have to. I know alot of labs where people have to share everything but I don’t encourage this practice.CONSERVATION PHILOSOPHYThe modern preparator’s obsession with the subject of “glue” is a good thing. Thediscussions can get tedious, repetitive, passionate, and personal beyond reason, but it hasresulted in a much more reasoned and disciplined approach to our work. In fact, it’sunfortunate that more preparators don’t obsess about it. Thinking more about what weuse and how we use it is good for the specimens and that is the bottom line.8

This leads me to the next topic that should be learned and learned well; the appropriateuse and application of various adhesives and consolidants. This skill is both the hardestand most critical thing you will need to learn. While I have my personalrecommendations, my first advice is to avoid being dogmatic in your approach tomaterials (and skeptical of those who are). Have an open mind; be well informed,creative, and ready to think outside the box. Use materials and techniques because theymake sense, not because they happen to be lying around the lab or the last person usedthem.Most of us are neither chemists nor conservation materials experts and must thereforerely on studies done by these specialists for much of our information on the properties ofthese materials. I am a firm advocate of rigorous testing and the need for comparativestudies of all of the adhesives and consolidants that have been used in preparation. But Ialso believe that important evidence indicating the effectiveness and longevity of theseproducts rests on the shelves of museum collections around the world and we should bepaying more attention to that. I am also wary of generalized statements regarding what is“best.” For instance, of the typical solvent-based systems in use today, I’ve found that itis very hard to compare and contrast Acryloid B-72, Butvar (B-76), or PVA (B-15)because there is an infinite range of ways to mix them in multiple solvents.I am my own worst critic and when I look at my own past work my eyes are drawn to theflaws. Learn from your mistakes and especially from those of others so you can avoidmaking them in the first place. Whenever I look at museum collections I look for flawsin preparation technique and materials, particularly adhesive and “filler” failures, and askquestions about the materials that were used. Look for clues like loose pieces and peelingof adhesive materials from bone and rock. These features usually indicate shrinkage ofthe material that can be catastrophic for microfossils. Note what has worked well forothers and steal all the ideas you can. Seek out the most reliable materials with provenlong term track records. Buying the cheap stuff off the shelf at the local hardware store isusually not the best way to go. The online PREPLIST is the best place to find the mostup to date information and explore options (see References and Resources section).Regardless of what you use, I recommend that the user of any substance pay attention toinstructions, labels, MSDS, and product brochures that come with them. No chemicalthat we use for prep is made specifically for our use and contents can be changed withoutwarning; this includes many of the adhesives advocated by the conservation community.My personal revelation concerning this issue involved Duco cement, an adhesivecommonly used by many as a bonding agent in the field and lab. It was also universallycondemned by conservators (justly so) for being a cell

“Wax on, wax off” - the Micropreparator mindset No, the title to this paper does not refer to Carbowax, paraffin, or beeswax. It refers to the degree of focus, control, and discipline required to practice microprep and how that can have a meditative, almost Zen-

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